As I've been saying about the Apps-walled-gardens problem for years:
The best way to fight is:
Use services via websites & browser.
The principle: use it or lose it.
You _have_ to give companies a financial incentive to keep services accessible via websites.
You _have_ to give managers statistics that say: we've had 30 % of interactions with our service via the website, we cannot lose this.
If people 95 % opt for the App, because "muh, App has so much better UI/UX than browser" they'll turn off websites as soon as they can.
Same goes for websites working with Firefox/derivatives: if you want maintainers to make sure their websites work well with FF, you have to use FF and thus flood their servers with your FF user agent.
If shops risk missing revenue by their website not working for people with buying power .. they will make sure their site works with the browser.